Spirochetes and Spiral Bacteria (Treponema/Syphilis, Borrelia/Lyme Disease and Relapsing Fevers, Leptospira, Campylobacter, Helicobacter)
8 topics with a brief review: definitions, key facts, and classroom questions.
Welcome to the section dedicated to spirally curved bacteria with unique motility. Here, we analyze pathogens that cause both classic sexually transmitted infections and dangerous vector-borne and zoonotic diseases.
The material covers Treponema pallidum (the causative agent of syphilis) and non-venereal treponematoses, Borrelia (Lyme disease) and relapsing fevers, as well as Leptospira. Campylobacter, a frequent cause of acute intestinal infections, and the microbiological aspects of bacterial vaginosis are discussed separately.
During classes and exams, professors are sure to ask about the structural features of spirochetes (endoflagella, fibrils), methods for their detection (silver impregnation, dark-field microscopy), and the lack of growth on simple media. Pay special attention to the serological diagnosis of syphilis (non-treponemal and treponemal tests)—this is a classic stumbling block on tests—as well as the transmission routes of borreliosis and leptospirosis.
Why is it important to evaluate specifically the concentration of Gardnerella vaginalis during molecular diagnostics?
These bacteria are normally present in the biocoenosis in small amounts. Only a sharp increase in their titer indicates the development of bacterial vaginosis.
Why is the causative agent called "pale" treponema?
Due to the structural features of its cell wall, the bacterium takes up stains very poorly. With classical Romanowsky-Giemsa staining, it acquires only a pale, barely perceptible pink hue.
How do non-venereal treponematoses differ from venereal syphilis?
The main differences lie in the routes of transmission (predominantly contact-based or vector-borne) and strict geographical restriction to the tropics, Asia, or Africa.
Why are joints affected upon infection?
This is due to autoimmune reactions. At 37 °C, the bacterium produces a heat shock protein identical to a human one, causing the immune system to attack its own tissues (molecular mimicry).
Can one contract epidemic typhus directly from a louse bite?
No, infection occurs via contamination—when scratching the skin, a person rubs the hemolymph of a crushed insect into microtraumas.
How does a person contract leptospirosis?
The main route of transmission is waterborne, through swimming in contaminated bodies of water or consuming polluted water. Alimentary and contact routes are also possible.
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